Embodiments of the present invention relate generally to low voltage lighting systems, and more particularly, to a low voltage lighting system having a soft-start.
Low Voltage lighting systems typically include a switch, a transformer or other voltage reduction device and one or more lighting elements or lamps. The switch may be a timer, a photocell, a single on-off light switch, or another suitable switching device. The transformer provides voltage reduction of incoming alternating current (AC) voltage.
In an incandescent lamp, an electric current passes through a thin filament, heating the filament and causing it to emit light. When the lamp is off the filament resistance is one tenth of the hot resistance. The power delivered to the lamp during startup (i.e., when the switch is first closed and a voltage is applied across the filament) is extremely high, causing a lamp surge current. A magnetizing current on the transformer on startup can also be very high, which causes a transformer surge current. The two surge currents may cause some circuit breakers to false trip at startup. Additionally, the current surge during startup causes a thermal shock to the lighting elements. In the winter, when the lamp is initially colder while it is off, the rapid change in temperature on startup is greater and lamp failure occurs much more frequently. With a conventional incandescent lamp, surge protectors are sometimes used in order to mitigate the effects of surge currents. However, the surge protectors use additional power, causing surge protector losses.
It is desirable to provide a soft-start low voltage lighting system that controls the power during turn-on so that lamp and transformer surge current are reduced or eliminated and false breaker trips are eliminated. It is desirable to provide a soft-start low voltage lighting system that warms up the lamp slowly, reducing or eliminating failures due to thermal shock. It is desirable to provide a soft-start low voltage lighting system that eliminates the need for a surge protector, thereby eliminating surge protector losses.